1. Field of the Invention
The invention relates to devices comprising carbon nanotube films.
2. Discussion of the Related Art
Carbon nanotubes have interesting electronic properties and offer potential for use in electronic devices and in interconnect applications. Carbon nanotubes also feature high aspect ratios (&gt;1000) and atomically sharp tips which make them ideal candidates for electron field emitters. To realize these potential applications, there is a need to process nanotubes into useful forms such as thin films, and, advantageously, patterned thin films.
Carbon nanotubes are currently being produced by a variety of different techniques such as arc-discharge, laser ablation and chemical vapor deposition (CVD). (See S. Iijima, Nature, Vol. 354, p. 56 (1991); T. W. Ebbesen and P. M. Ajayan, Nature, Vol. 358, p. 220 (1992); and B. I. Yakobson and R. E. Smalley, American Scientists, Vol. 85, p. 324 (1997). The as-deposited material, however, is usually in the form of loose powders, porous mats, or films with poor adhesion. These forms of nanotubes do not lend themselves to convenient preparation of robust adherent nanotube thin film structures. The difficulty in preparing an adherent film of nanotubes is believed to be due to the perfect structure associated with carbon nanotubes, which contain essentially no dangling bonds and few defect sites. As a result, nanotube films tend to exhibit poor adhesion, even to the point of being easily removed by contact or by air flow (e.g., an air duster).
Patterned nanotube films have been reported by Fan et al., Science, Vol. 283, p. 512 (1999), and Xu et al., Appl. Phys. Lett., Vol. 74, p. 2549 (1999). These references describe use of direct deposition techniques such as CVD, in which substrates are selectively patterned with catalyst metals and then nanotubes are grown in the patterned areas. These techniques, however, produce films with poor adhesion. The techniques also expose the substrates to a reactive and high-temperature deposition environment, which is both inconvenient and harmful to actual device structures. In addition, the techniques are limited to the patterned growth of multi-wall carbon nanotubes (MWNTs), because CVD typically produce MWNTs on catalytic substrates.
Thus, there is a desire to develop more convenient and versatile methods for patterning carbon nanotube films with adequate adhesion, to allow formation of more useful and robust device structures.